1. Field of the Invention
This invention relates to a fluid apparatus, more specifically a blower which can ventilate in opposite directions.
2. Background Art
Ventilation is necessary by means of a fluid apparatus such as an axial flow blower, for example, in a tunnel 81 at a highway, as shown in FIG. 8 of the accompanying drawings. The blower 82 sends wind up and down the road in accordance with traffic volume and atmospheric pressure at the entrance and the exit of the tunnel 81, so that the tunnel 82 is ventilated effectively and economically.
Two types of blowers have been widely known for such ventilation. One is, as shown in FIG. 9, a blower provided with fixed moving blades 91 of rectangular section. This blower sends wind bidirectionally by only changing the direction of rotation of a blade wheel (not shown) which the blades 91 are attached to. The other one is, as shown in FIG. 10, a blower with rotatable moving blades 101 of streamline section. When changing the direction of ventilation by this blower, the blade wheel is rotated in a reverse sense and the blades 101 are also rotated about their respective axes approximately 180 degrees. However, in the former case, the moving blade has a rectangular section so that the resulting noise is large and ventilation efficiency is low. In addition, it consumes electric power nearly 10% more than the latter blower. On the other hand, in the later case, a complicated drive mechanism (not shown) is required to rotate the moving blades 101 about the axes thereof. Thus it is very costly.